Video signal recording and reproducing apparatus

ABSTRACT

The video signal recording and reproducing apparatus of the invention includes: a receiving section for receiving a television signal; an image compression section for compressing an amount of information per unit time of the received continuous video signal; a writing section for intermittently writing a compressed video signal, obtained as an output of the image compression section, onto a hard disk apparatus via a magnetic head; a reading section for intermittently reading out the written compressed video signal from the hard disk apparatus via the magnetic head; a decoding section for restoring the read compressed video signal into an original video signal; a display section for displaying the restored video signal; and a control section for controlling the writing section and the reading section such that writing the video signal onto the hard disk apparatus and reading an arbitrary video signal, which was previously written onto the hard disk apparatus, from the hard disk apparatus are performed apparently simultaneously and continuously.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a video signal recording andreproducing apparatus which can simultaneously record and reproduce avideo by using a disk apparatus.

[0003] 2. Description of the Related Art

[0004] A video tape recorder (VTR) has heretofore been used as ahome-use video recording apparatus. As is well known, a VTR receives abroadcast program transmitted by a broadcasting station via an antenna,records the program and then reproduces the program. That is to say,having once finished the recording operation of a predetermined program,the VTR rewinds the tape on which the program has been recorded and thenreproduces the received and recorded program to be watched.

[0005] A currently available VTR cannot record and reproduce a videosimultaneously. For example, assuming that a broadcast program whichstarts at 10 o'clock and ends at 12 o'clock is now being received andrecorded by a single VTR, it is impossible to reproduce and watch thebroadcast program from the beginning from 11 o'clock on, whilecontinuing receiving and recording the program. It is much lessimpossible to perform a trick play reproducing operation (e.g., afast-forward reproducing operation or a backward reproducing operation)of a recorded video of a program which is now being received andrecorded. On the other hand, a technique which is called “followingreproducing operation” is currently utilized for a live broadcastrelayed by a broadcasting station. In accordance with this technique, avideo which has been transmitted to a broadcasting station is slightlydelayed and then delivered substantially in real time. However, in sucha case, it is necessary to use either a plurality of VTRs or an opticaldisk apparatus of a special type in which a recording head and areproducing head are separately provided, for simultaneously performingthe recording and the reproducing operations. If a plurality of VTRs aresimultaneously used, then it becomes adversely complicated to operatethese apparatuses. On the other hand, the use of such an optical diskapparatus of a special type disadvantageously increases the costs.

SUMMARY OF THE INVENTION

[0006] According to the present invention, a video signal recording andreproducing apparatus is provided. The video signal recording andreproducing apparatus of the invention includes: receiving means forreceiving a television signal; image compression means for compressingan amount of information per unit time of the received continuous videosignal, writing means for intermittently writing a compressed videosignal, obtained as an output of the image compression means, onto ahard disk apparatus via a magnetic head; reading means forintermittently reading out the written compressed video signal from thehard disk apparatus via the magnetic head; decoding means for restoringthe read compressed video signal into an original video signal; displaymeans for displaying the restored video signal; and control means forcontrolling the writing means and the reading means such that writingthe video signal onto the hard disk apparatus and reading an arbitraryvideo signal, which was previously written onto the hard disk apparatus,from the hard disk apparatus are performed apparently simultaneously andcontinuously.

[0007] In one embodiment, a compressed video signal which was recordedat an earliest time is sequentially updated by a newly received andobtained compressed video signal.

[0008] In another embodiment, an audio signal, as well as a compressedvideo signal, is recorded onto the hard disk apparatus.

[0009] In still another embodiment, the video signal recording andreproducing apparatus further includes instruction means for startingand/or finishing recording a compressed video signal onto the hard diskapparatus.

[0010] In still another embodiment, the video signal recording andreproducing apparatus further includes instruction means for startingand/or finishing reproducing a compressed video signal from the harddisk apparatus.

[0011] In still another embodiment, the instruction means for startingrecording a compressed video signal onto the hard disk apparatus isinstantaneously driven manually.

[0012] In still another embodiment, the instruction means for startingrecording a compressed video signal onto the hard disk apparatus isdriven by timer means.

[0013] In still another embodiment, the instruction means for finishingrecording a compressed video signal onto the hard disk apparatus isdriven by timer means.

[0014] In still another embodiment, the instruction means for startingreproducing a compressed video signal from the hard disk apparatus isinstantaneously driven manually.

[0015] In still another embodiment, the display means displays at leasta time difference between a time at which a video signal which is beingreproduced was recorded and a current time, in addition to a video.

[0016] In still another embodiment, the display means displays at leasta current time and a time at which a video signal which is beingreproduced was recorded, in addition to a video.

[0017] In still another embodiment, the video signal recording andreproducing apparatus includes operation means for setting a normalreproduction, a fast forward reproduction, a backward reproduction or aslow reproduction as a reproduction mode.

[0018] In still another embodiment, the display means simultaneouslydisplays a received video signal and an output of the decoding meanswhich was previously recorded, reproduced and decoded.

[0019] In still another embodiment, the video signal recording andreproducing apparatus further includes television signal detection meansfor determining whether or not the receiving means has received a normaltelevision signal and writing onto the hard disk apparatus is enabledonly when the television signal detection means has detected a normaltelevision signal.

[0020] According to another aspect of the present invention, a videosignal recording and reproducing apparatus is provided. The video signalrecording and reproducing apparatus includes: image compression meansfor digitizing an input continuous video signal and audio signal,thereby compressing an amount of information per unit time; writingmeans for intermittently writing a compressed video signal, obtained asan output of the image compression means, onto a hard disk apparatus viaa magnetic head; reading means for intermittently reading out thewritten compressed video signal from the hard disk apparatus via themagnetic head; decoding means for restoring the read compressed videosignal into an original video signal; and display means for displayingthe restored video signal, thereby reading out predetermined video andaudio signals at a predetermined time.

[0021] According to still another aspect of the present invention, avideo signal recording and reproducing apparatus is provided. The videosignal recording and reproducing apparatus includes: image compressionmeans for digitizing an input continuous video signal and audio signal,thereby compressing an amount of information per unit time; writingmeans for intermittently writing a compressed video signal, obtained asan output of the image compression means, onto a hard disk apparatus viaa magnetic head; reading means for intermittently reading out thewritten compressed video signal from the hard disk apparatus via themagnetic head; decoding means for restoring the read compressed videosignal into an original video signal; display means for displaying therestored video signal; and sound recognition means for recognizing anaudio signal. In the video signal recording and reproducing apparatus,predetermined video and audio signals are read out at a point of timewhen the sound recognition means recognizes a predetermined sound.

[0022] According to still another aspect of the present invention, avideo signal recording and reproducing apparatus is provided. The videosignal recording and reproducing apparatus includes: image compressionmeans for digitizing an input continuous video signal and audio signal,thereby compressing an amount of information per unit time; writingmeans for intermittently writing a compressed video signal, obtained asan output of the image compression means, onto a hard disk apparatus viaa magnetic head; reading means for intermittently reading out thewritten compressed video signal from the hard disk apparatus via themagnetic head; decoding means for restoring the read compressed videosignal into an original video signal; and display means for displayingthe restored video signal. In the video signal recording and reproducingapparatus, a video signal at an arbitrary point of time is retrieved foran arbitrary time period by an operation of a viewer from video signalswhich are being received or video signals which were previouslyrecorded, and information for prohibiting overwriting data of theretrieved video signal is added to the retrieved video signal so as tobe stored into the hard disk apparatus.

[0023] In one embodiment, when a video signal retrieved by an operationof a viewer is saved, search information required for the viewer tosearch for a desired video signal later is added to the video signal tobe saved, and after the video signal which was previously retrieved andsaved has been searched for and read out based on the searchinformation, the read compressed video signal is decoded to be displayedon the display means.

[0024] In another embodiment, the video signal recording and reproducingapparatus includes at least an output terminal for outputting digitaldata which has been recorded onto the hard disk apparatus to the outsideof the apparatus. In the video signal recording and reproducingapparatus, a video signal retrieved by a viewer is transferred toanother recording apparatus through the output terminal.

[0025] According to still another aspect of the present invention, avideo signal recording and reproducing apparatus is provided. The videosignal recording and reproducing apparatus includes: image compressionmeans for digitizing an input continuous video signal and audio signal,thereby compressing an amount of information per unit time; writingmeans for intermittently writing a compressed video signal, obtained asan output of the image compression means, onto a hard disk apparatus viaa magnetic head; reading means for intermittently reading out thewritten compressed video signal from the hard disk apparatus via themagnetic head; decoding means for restoring the read compressed videosignal into an original video signal; and display means for displayingthe restored video signal. In the video signal recording and reproducingapparatus, while compressing a video signal which is being received andwriting the compressed video signal onto the hard disk apparatus, avideo signal which was previously recorded is read out and decoded intoan original video signal, and after an amount of data of the decodedvideo signal has been reduced, the video signal is subjected to an imagecompression again and written onto the hard disk apparatus.

[0026] According to still another aspect of the present invention, avideo signal recording and reproducing apparatus is provided. The videosignal recording and reproducing apparatus includes: receiving means forsimultaneously receiving television signals from a plurality ofchannels; image compression means for compressing an amount ofinformation per unit time of the received continuous video signals fromthe plurality of channels; writing means for intermittently writing eachcompressed video signal, obtained as an output of the image compressionmeans, onto a hard disk apparatus via a magnetic head; reading means forintermittently reading out the written compressed video signal from thehard disk apparatus via the magnetic head; decoding means for restoringthe read compressed video signal into an original video signal; anddisplay means for displaying the restored video signal. In the videosignal recording and reproducing apparatus, while compressing videosignals from the plurality of channels which are being received andwriting the compressed video signals onto the hard disk apparatus, avideo signal which was previously recorded from a particular channel isread out.

[0027] According to still another aspect of the present invention, avideo signal recording and reproducing apparatus is provided. The videosignal recording and reproducing apparatus includes: receiving means forsimultaneously receiving television signals from a plurality ofchannels; synthesis means for synthesizing the received televisionsignals from the plurality of channels into one screen; imagecompression means for compressing an amount of information per unit timeof the continuous video signal which has been synthesized by thesynthesis means; writing means for intermittently writing a compressedvideo signal, obtained as an output of the image compression means, ontoa hard disk apparatus via a magnetic head; reading means forintermittently reading out the written compressed video signal from thehard disk apparatus via the magnetic head; decoding means for restoringthe read compressed video signal into an original video signal; anddisplay means for displaying the restored video signal. In the videosignal recording and reproducing apparatus, a plurality of video signalsare synthesized into one screen, subjected to an image compression andthen written onto the hard disk apparatus.

[0028] By utilizing the above-described configurations, it is possibleto provide an apparatus which can independently perform a trick playreproducing operation (e.g., a fast-forward reproducing operation or abackward reproducing operation) of a recorded part of a broadcastprogram which is now being received, while compression encoding andrecording the broadcast program. As a result, it is possible to startwatching a recorded part of a program without waiting for the program toend as is done in the recording and reproducing operations performed bya conventional single VTR. In addition, even when a viewer initiallystarts watching a program at a time much later than the broadcast starttime of the program, the viewer can finish watching the programsubstantially at the same time as the broadcast end time by additionallyutilizing a fast-forward reproducing function in the middle of thereproducing operation.

[0029] According to the present invention, it is possible to provide anapparatus which can perform a normal reproducing operation or a trickplay reproducing operation (e.g., a fast-forward reproducing operationor a backward reproducing operation) of a recorded part of a broadcastprogram which is now being received, while recording the broadcastprogram by using a universal hard disk apparatus without using aplurality of VTRs or an expensive optical disk apparatus for which arecording head and a reproducing head are separately provided. As aresult, it is possible to start watching a recorded part of a programwithout waiting for the program to end, as is necessary in the recordingand reproducing operations performed by a conventional single VTR. Inaddition, even when a viewer initially starts watching a program at atime much later than the broadcast start time of the program, the viewercan finish watching the program substantially at the same time as thebroadcast end time by additionally utilizing a fast-forward reproducingfunction in the middle of the reproducing operation, so that aconsiderable amount of time can be saved. Moreover, in the case where aviewer cannot help stopping watching a program in the middle of theprogram, even if the program still continues when the viewer resumeswatching the program, the viewer can reproduce and watch the programfrom the scene which was broadcast when the viewer left, whilecontinuing recording the program. Furthermore, in the case where aviewer watches a first program while recording a second program on adifferent channel, it is possible to instantaneously start watching thesecond program from the beginning thereof at a time after the firstprogram ends and before the second program ends.

[0030] Thus, the invention described herein makes possible the advantageof providing a video signal recording and reproducing apparatus whichcan simultaneously record and reproduce a television signal.

[0031] This and other advantages of the present invention will becomeapparent to those skilled in the art upon reading and understanding thefollowing detailed description with reference to the accompanyingfigures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]FIG. 1 is a block diagram illustrating a configuration for a videosignal recording and reproducing apparatus in a first example of thepresent invention.

[0033]FIG. 2 is a diagram illustrating an operational concept in thefirst example.

[0034]FIG. 3 is a diagram illustrating the contents of a table RAM.

[0035]FIG. 4 is a detailed timing chart of peripheral hardware for ahard disk apparatus.

[0036]FIG. 5 is a block diagram illustrating a configuration for a videosignal recording and reproducing apparatus in a fourth example of thepresent invention.

[0037]FIG. 6 is a block diagram illustrating a configuration for a videosignal recording and reproducing apparatus in a sixth example of thepresent invention.

[0038]FIG. 7 is a diagram illustrating a screen synthesis in the sixthexample of the present invention.

[0039]FIG. 8 is a diagram illustrating a screen separation in the sixthexample of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] Hereinafter, the embodiments of the present invention will bedescribed with reference to the accompanying drawings.

EXAMPLE 1

[0041]FIG. 1 is a block diagram illustrating a configuration for a videosignal recording and reproducing apparatus in a first example of thepresent invention. In FIG. 1, the reference numeral 1 denotes anantenna; 2 denotes a tuner; 3 denotes a demodulator; 4 denotes an MPEG1encoder; 5 and 6 denote recording buffer memories; 7 denotes a firstswitch; 8 denotes a hard disk apparatus; 9 and 10 denote reproducingbuffer memories; 11 denotes a second switch; 12 denotes an MPEG1decoder; 13 denotes a TV monitor; 14 denotes a hard disk controller; 15denotes a table RAM; 16 denotes a system controller; 17 denotes a timer;and 18 denotes an operator panel.

[0042] First, before describing the operation of the apparatus in thefirst example with reference to FIG. 1, the operational concepts will bedescribed with reference to FIG. 2. In this example, it is assumed thata viewer wants to watch a program which is to be broadcast from 10 p.m.to 12 p.m. (as shown in portion (a) of FIG. 2) but that it is only after11 p.m. that the viewer can watch the program because of someinconvenience. In such a case, in accordance with the method of thisexample, while recording the program from 10 p.m. to 12 p.m. (as shownin portion (b) of FIG. 2), the viewer can start reproducing the programfrom the beginning thereof from 11 p.m. (as shown in portion (c) of FIG.2). When a normal reproducing mode is selected, the reproducingoperation ends at 1 a.m. which is two hours later than the time when theviewer started watching the program. On the other hand, since afast-forward reproducing operation can also be performed on a part ofthe program which has already been recorded as shown in portion (d) ofFIG. 2, it is also possible to reproduce all of the program at a timeslightly later than 12 p.m., that is the time when the broadcasting ofthe program actually ends.

[0043] Hereinafter, a detailed operation of the video signal recordingand reproducing apparatus of the first example will be described withreference to FIG. 1. First, a viewer pre-sets a TV channel, a recordingstart time and a recording end time of a program to be watched on theoperator panel 18. For example, it is assumed that the viewer sets aprogram on channel # 6 starting at 10 p.m. In such a case, when it is 10p.m., the system controller 16 sets the tuner 2 to channel # 6 inaccordance with the information supplied from the timer 17 such that theelectric waves for the channel # 6 are selected from the electric wavesreceived by the antenna 1, and the demodulator 3 demodulates thereceived waves into signals.

[0044] The received signals can be monitored on the TV monitor 13. Thereceived signals are converted by the MPEG1 encoder 4 into compressedvideo signals so as to be bit streams having a bit rate of 1.5 Mbps.These signals are transmitted via the first and the second recordingbuffer memories 5 and 6 having a capacity of 200 Kbytes, for example,and the first switch 7 so as to be written onto the hard disk apparatus8.

[0045] This operation will be described in detail later with referenceto FIG. 3. The sector information indicating the physical positions ofthe compressed video signals written on the hard disk and the timeinformation of the written signals are stored in the table RAM 15 so asto correspond to each other. Such a state is maintained until 11 p.m.,when the viewer starts watching the program. When it is 11 p.m., theviewer starts watching the program on the TV monitor 13. In this case,if the viewer wants to watch the program starting at 10 p.m. (i.e.,reserved recording start time) from the beginning thereof, then theviewer has only to push the reproducing button (not shown) on theoperator panel 18.

[0046] In this case, the program starting at 10 p.m. is reproduced fromthe beginning thereof from 11 p.m. at a normal reproducing speed asshown in portion (c) of FIG. 2. The hard disk controller 14 controls thehard disk apparatus 8 in accordance with the information supplied fromthe table RAM 15, so that the compressed video signals recorded on thehard disk apparatus 8 are reproduced via the reproducing buffer memories9 and 10 and the second switch 11. This operation will be described indetail later with reference to FIG. 3. The reproduced compressed videosignals are decoded by the MPEG1 decoder 12 so as to be video signalswhich are displayed on the TV monitor 13.

[0047] It is noted that, in this example, the video signals compressedby the MPEG1 encoder 4 are being transmitted via the recording buffermemories 5 and 6 and the first switch 7 so as to be continuously writtenonto the hard disk apparatus 8 until 12 p.m. during the reproduction ofthe video signals. When it is 12 p.m., the system controller 16 finishesrecording the compressed video signals onto the hard disk apparatus 8 inaccordance with the information supplied from the timer 17. In thiscase, it is possible to monitor on the TV monitor 13, the video signalswhich are being written in parallel with the video signals which arebeing reproduced by using a technique such as a screen division.

[0048] On the other hand, in performing the reproducing operation, theviewer can reproduce a part of a program to be watched in detail at aslower speed and can reproduce an unnecessary part of the program at ahigher speed in accordance with the instructions supplied from thesystem controller 16 by operating the operator panel 18. Thecorrespondence between the sector information of the compressed videosignals recorded on the hard disk, and the time information of thesignals, has been stored in the table RAM 15 for performing theseoperations.

[0049] The format of this table is shown in FIG. 3. In FIG. 3, thereference numeral 19 denotes the time information represented as a timecode and 20 denotes a sector number on the hard disk. In this example,since each of a plurality of successive sectors corresponds to onesecond, sector addresses are indicated every other second in FIG. 3. Inaccordance with the operation of the viewer, the hard disk controller 14reproduces required video signals based on this time information.

[0050] In the case of the MPEG1 standard, an image is generallycompressed based on a unit consisting of a plurality of frames. Aconcept “GOP (group of pictures)” is used as the unit. For example, inthe case where 1 GOP=15 frames, 1 GOP covers a video corresponding to0.5 second. Thus, in the case of performing a fast forward reproducingoperation or a slow reproducing operation, if a decimation or aninterpolation is performed on a GOP basis with respect to a video whichhas been decoded on a GOP basis, the resulting motion of the image is nolonger smooth. In order to make the motion smooth, the decimation or theinterpolation is required to be performed on a frame basis.

[0051] That is to say, a 10× fast-forward reproducing operation (or afast-forward reproducing operation performed at a speed ten times ashigh as a normal reproducing speed) is realized by reproducing one frameout of ten frames. On the other hand, a {fraction (1/10)}× slowreproducing operation is realized by displaying one and the same frame10 times in succession.

[0052] A time difference between the time when the video which is nowbeing reproduced was recorded (hereinafter, such a time will be referredto as a “video recording time”) and the current time, can be calculatedby subtracting the video recording time, obtained by using the timeinformation supplied from the table RAM 15, from the current time. Ifthe time difference is displayed on the TV monitor 13, the timedifference can be monitored. Before this time difference becomes zero,any arbitrary part of the video which has already been recorded can bereproduced. In addition, it is also possible to simultaneously displayon the TV monitor 13 both the time corresponding to the output of thedemodulator 3 and the time corresponding to the output of the MPEG1decoder 12 by dividing the screen into two parts. Then, a video which isnow being broadcast (and corresponds to the output of the demodulator 3)and a video which is now being reproduced (and corresponds to the outputof the MPEG1 decoder 12) can be simultaneously watched on the samescreen.

[0053] Assuming that the hard disk apparatus has a capacity large enoughto record compressed video signals corresponding to two hours, if theviewer does not start watching a program within two hours after therecording start time, the recorded signals are updated from the point oftime two hours later than the recording start time, whereby a programcorresponding to two hours preceding the time when the viewer startswatching the recorded program can always be covered. On the other hand,an update halt mode may also be selected. In such a case, a video canonly be recorded for two hours in the same way as a commonly used VTR.

[0054] Hereinafter, detailed timings of peripheral hardware of the harddisk apparatus 8 will be described with reference to FIG. 4.

[0055] The detailed configuration of the hard disk apparatus 8 isomitted in FIG. 1. A hard disk apparatus which is universally used as aperipheral device for a computer system can be used as the hard diskapparatus 8. The hard disk apparatus 8 may include either one diskmedium or a plurality of disk media and includes a recording andreproducing head, not a head exclusively used for a recording operationor a reproducing operation.

[0056] Portion (a) of FIG. 4 represents an output of the MPEG1 encoder 4and A1, A2, A3, . . . A6 indicate the signals obtained by dividing theoutput by every 1.5 Mbits. Portion (b) of FIG. 4 represents theoperational modes of the recording buffer memory 5 having a capacity of200 Kbytes and W indicates writing a signal onto the memory and Rindicates reading out a signal from the memory. Thus, A1-W means writinga signal A1 onto the buffer memory and A1-R means reading out the signalA1 from the buffer memory, for example. A signal is written onto thebuffer memory in real time simultaneously with the video signals, whilethe signal is read out from the buffer memory at a high rate inaccordance with the transfer rate at which the signal is transferred tothe hard disk apparatus 8.

[0057] Portion (c) of FIG. 4 represents the operational modes of therecording buffer memory 6 having a capacity of 200 Kbytes and W and Rindicate the same operations as those in portion (b). The buffermemories 5 and 6 operate in pairs. More specifically, while one of thebuffer memories 5 or 6 transfers data to the hard disk apparatus 8 viathe first switch 7, the other buffer memory 6 or 5 stores therein acompressed video signal supplied from the MPEG1 encoder 4.

[0058] Portion (d) of FIG. 4 represents the seek timings for writingdata onto the hard disk apparatus 8. Portion (e) of FIG. 4 representsthe timings at which data is transferred from the buffer memories 5 and6 to the hard disk apparatus 8 so as to be written thereon. A1-W meanswriting the signal A1 onto the hard disk apparatus 8. Though the timesequence is not specifically shown in FIG. 4, portions (b) and (c)always precede portion (e). For example, the signal A1 read out by A1-Rin portion (b) is written by A1-W in portion (e).

[0059] Portion (f) of FIG. 4 represents the seek timings for reading outdata from the hard disk apparatus 8. Portion (g) of FIG. 4 representsthe timings at which data is read out from the hard disk apparatus 8 andB1-R means reading out a signal B1 from the hard disk apparatus 8, forexample. Portion (h) of FIG. 4 represents the operational modes of thereproducing buffer memory 9 having a capacity of 200 Kbytes and B1-Wmeans writing the signal B1 onto the buffer memory 9.

[0060] Portion (i) of FIG. 4 represents the operational modes of thereproducing buffer memory 10 having a capacity of 200 Kbytes and W and Rindicate the same operations as those described above. The buffermemories 9 and 10 operate in pairs. More specifically, while a signalread out from the hard disk apparatus 8 is written onto one of thebuffer memories 9 or 10, the other buffer memory 10 or 9 reads out asignal, which has been supplied from the hard disk apparatus 8 andstored in the buffer memory 10 or 9, at a rate of the video signal andthen supplies the signal to the MPEG1 decoder 12 via the second switch11.

[0061] Portion (j) of FIG. 4 represents an input to the MPEG1 decoder12. As shown in FIG. 4, the input has been extended so as to have thesame period as that of the output in portion (a) and is continuouslyreproduced.

[0062] As shown in FIG. 4, for recording and reproducing a video signalsimultaneously and continuously, the period of each of the signals A1,A2, A3, . . . is set to be longer than the following time T:

[0063] T=(seek time for preparing to record data onto the hard disk)

[0064] +(time required for writing the data having the period onto thehard disk)

[0065] +(seek time for preparing to reproduce the data from the harddisk)

[0066] +(time required for reading out the data having the period fromthe hard disk)

[0067] If the total of these times becomes longer than the period of A1,A2, A3, . . . , then the video cannot be recorded but overflows. Thus,the period is required to be sufficiently longer than the total time.Since the seek time of the hard disk, in particular, largely variesdepending upon situations, a maximum seek time is required to beestimated and included in the sum.

[0068] In this case, the period of A1, A2, A3, . . . is a time duringwhich an MPEG bit stream having a bit rate of 1.5 Mbps is occupied by abuffer memory having a capacity of 200 Kbytes: 200 k÷(1.5 M÷8)=1 about 1second. Assuming that the data transfer rate of the hard disk is 1 Mbyteper second, the time required for transferring the data is: 200 k÷1M=0.2 second. Even when the maximum seek time is estimated to be 100milliseconds,

T=0.1+0.2+0.1+0.2=0.6 second <1 second

[0069] Thus, a sufficient margin time can be obtained.

[0070] As described above, the video signal recording and reproducingapparatus according to the present invention is a video signal recordingand reproducing apparatus using a hard disk which can simultaneouslyperform the recording and reproducing operations in different portionsof the same hard disk. Thus, it is possible to provide an apparatuswhich can perform a trick play reproducing operation (e.g., afast-forward reproducing operation or a backward reproducing operation)of a recorded part of a broadcast program which is now being recorded,while recording the broadcast program.

[0071] As a result, it is possible to start watching the recorded partof a program without waiting for the program to end, as is necessary inthe recording and reproducing operations performed by a conventionalsingle VTR. In addition, even when a viewer initially starts watching aprogram at a time much later than the broadcast start time of theprogram, the viewer can finish watching the program substantially at thesame time as the broadcast end time by additionally utilizing afast-forward reproducing function in the middle of the reproducingoperation, so that a considerable amount of time can be saved.

[0072] Furthermore, though audio signal recording and reproducingsections are not shown in FIG. 1, a sound accompanied with a video canbe processed completely in the same way as the video. Therefore, thesame description as applied to a “video” in this example is applicableto “video and sound”.

[0073] It is noted that it is possible to perform the writing operationonto a hard disk only when it is necessary while a viewer watches a TVprogram for using the hard disk as long as possible. In such a case, aviewer starts a video recording operation by pushing an instructionbutton. A recording start button and a reproducing start button areprovided for the operator panel 18 or a single button can be used forthese two purposes. This function is effectively applicable to a casewhere a viewer cannot help stopping watching a TV program in the middleof the program for some unavoidable reason. For example, in the casewhere it becomes necessary to stop watching a TV program in the middlefor receiving a visitor, responding to a telephone call, taking a bathor having a meal or the like, the viewer pushes the recording startbutton for recording the program from that point of time, settles hisbusiness and then pushes the reproducing start button. Thus, therecorded program is reproduced and the viewer can watch the program fromthe point of time when he started recording the program without missingany scene of the program. In addition, by providing an end settingbutton for allowing a viewer to set a recording end time easily, even ifthe viewer must go out suddenly and does not know exactly when he willbe able to come home, the viewer can record a video for as long as hewants. Thus, the viewer can comfortably leave after he sets the harddisk in a writing state. In this case, if the end setting button isconfigured such that the recording time can be set depending upon howmany times the viewer pushes the button (for example, one push of thebutton allows the program which is now being watched to be recorded for30 minutes and two pushes of the button allows the program to berecorded for 1 hour), then the viewer can advantageously operate thisapparatus very easily.

[0074] Since the program is continuously recorded during thereproduction of the program, the viewer can naturally watch the part ofthe program which is being broadcast during the reproduction.

[0075] In addition, a TV signal detector (not shown in FIG. 1) fordetermining whether or not a TV broadcast is available or not isincorporated in the demodulator 3 shown in FIG. 1. A synchronizingsignal detector which is commonly provided for an existing TV receivercan be used as the TV signal detector and it is not necessary toadditionally provide a novel circuit. Hereinafter, a case where asynchronizing signal detector is used as the TV signal detector will bespecifically described.

[0076] First, it is determined whether or not a synchronizing signalexists in the demodulated video signal. If a synchronizing signal isabsent in the demodulated video signal, then it is determined to be outof a broadcasting time, thereby protecting the hard disk apparatus fromthe writing operation. If the writing operation has already been startedon the hard disk apparatus, the writing operation onto the hard diskapparatus is temporarily suspended at a point of time when thesynchronizing signal is no longer detected and is resumed when thesynchronizing signal is detected again. As a result, it is possible toavoid performing a recording operation in an undesired time period(e.g., a midnight time or the like when no broadcast is available), sothat the lifetime of the hard disk apparatus can be lengthened. Thisfunction will be effective for avoiding performing an unnecessaryrecording operation at midnight when no broadcast is televised,supposing that a hard disk comes to have a recording capacity largeenough to always record a televised video corresponding 24 hourspreceding the current time in the near future. Since a synchronizingsignal detector is commonly available well known circuit, the detaileddescription thereof will be omitted herein. A synchronizing signaldetector of the type which integrates a synchronizing signal obtainedfrom a well known synchronizing signal separator thereby determiningwhether or not the DC level thereof is a normalized value, or asynchronizing signal detector of the type which determines whether ornot the frequency of the synchronizing signal is a predetermined value(e.g., the frequency of a horizontal synchronizing signal is 15.73 KHzin an NTSC standard) is used herein.

[0077] This example has been described while using a synchronizingsignal detector as a TV signal detector. However, in the case where adigital broadcast is received, the TV signal can be detected by a methodin which it is determined whether or not an error signal detected by anerror signal detector, used for reproducing a clock for a PLL or thelike, is at a predetermined level or by a method in which it isdetermined whether or not the amount of the error flag output from anerror detector for correcting an error of a transmitted signal is at apredetermined level.

[0078] If a viewer continuously records a program and supplies a signalby the push of a button or the like for stopping watching the programsuch that the recording stop time, the address and the like are stored;then the viewer can naturally reproduce the program from the point oftime when the viewer stopped watching the program by pushing thereproducing start button for resuming watching the program.

[0079] In addition, by additionally providing a second tuner and asecond demodulator (though not shown in FIG. 1), a channel to be watchedand a channel to be recorded can be independently designated. Forexample, a case where a second program to be watched by a viewer startson another channel while the viewer is watching a first program to berecorded will be assumed. In such a case, if the viewer starts to recordthe second program on the second channel, the viewer can watch thesecond program from the beginning thereof from the point of time whenthe first program which the viewer is watching ends.

EXAMPLE 2

[0080] Hereinafter, a second example of the present invention will bedescribed. Since the fundamental configuration in the second example issubstantially the same as that in the first example shown in FIG. 1, nodrawings will be particularly referred to for describing the secondexample.

[0081] The video signal recording and reproducing apparatus of thesecond example is further provided with a circuit for inputting a videoand/or a sound other than that of a broadcast (e.g., a reproduced signalof a VTR). If a part of a broadcast or desired video and/or sound inputthrough the circuit is stored in the hard disk apparatus 8 for about 10seconds and is automatically reproduced at a predetermined time everymorning, the broadcast or the video and/or the sound can be used inplace of an alarm clock so that a user can wake up comfortably.

[0082] It is noted that in such a case, the volume of the sound isrequired to be automatically adjusted to a sufficiently large volume,irrespective of a sound volume which was set the previous day.Furthermore, by additionally providing a speech recognition circuit forthe apparatus shown in FIG. 1, the apparatus can reproduce apredetermined video by recognizing the audible alarm of an alarm clockother than the clock incorporated in the system. Alternatively, byrecognizing not an alarm but a speech pattern such as “I'm home” when auser comes home, the apparatus can reproduce a predetermined video byreading the video from the hard disk apparatus 8.

[0083] Furthermore, it is true that a user is required to performcomplicated operations for designating his desired video and/or sound.However, if compressed video and/or sound are/is recorded in aninexpensive medium such as a floppy disk or a CD-ROM and the medium isput on the market, then the user can record his desired video and/or thesound onto the hard disk by connecting a reader for reading the videoand/or sound from the medium to this apparatus. If the user reproducesthe video and/or the sound at a predetermined time every morning, theuser can receive a morning call of his favorite actor or the like. Thus,this apparatus can also be used as an instrument for making a user'slife comfortable.

EXAMPLE 3

[0084] Hereinafter, a third example of the present invention will bedescribed. In this third example, the hard disk apparatus shown in FIG.1 has at least two recording regions. The first recording region of thehard disk apparatus 8 is a recording region in which the video signalreceived by the tuner 2 is recorded for realizing the function describedin the second example. The second recording region of the hard diskapparatus 8 is a recording region for saving therein the video datawhich has arbitrarily been retrieved by a viewer from the video datarecorded in the first recording region. As a result, the viewer canselectively save arbitrary information from a televised program in thesecond recording region while the viewer is watching the program.

[0085] For example, if only a scene of a travel program frequentlytelevised recently, in which the address, the telephone number and thelike of a hotel are displayed on the screen or the contents of a dish, aservice or the like are presented, is selectively saved in the secondrecording region, the viewer can save such information more exactlywithout any need for taking notes. In addition, if the viewer applies afile name to the video data retrieved by himself and then stored in aprescribed directory, the viewer will be able to search for his desiredfile later more easily.

[0086] A specific example will be described below. For example, thesecond recording region of the hard disk is divided beforehand into aplurality of directories for “restaurants”, “travel spots”, “hotels” andthe like. The directory of “hotels” can be further divided into aplurality of sub-directories of “restaurant hotels”, “hot-spring hotels”and the like. A viewer performs an operation for designating a startpoint and an end point of a video to be saved while the viewer iswatching a program, and then selects a directory corresponding to theretrieved data. As a result, the video data is automatically saved inthe selected directory. When the viewer searches for the video datalater, the viewer will be able to find the video data by selecting hisdesired directory and the file name of the video data. If an externaloutput terminal such as an SCSI interface is provided for the hard diskapparatus for storing the saved video data onto an external storagedevice such as a floppy disk drive or a PD drive, the viewer can producehis own database.

[0087] In this example, the hard disk apparatus is divided into tworecording regions for simplifying the description. Alternatively, thesame effects can also be attained by providing a circuit for designatingwhether the video data recorded on the hard disk is data which is to beautomatically updated or data which is not updated unless the viewercommands the update. For example, the hard disk apparatus can becontrolled by such a method that the type of recorded data, the sectorinformation and the like are recorded in the table RAM 15 shown in FIG.1 and the hard disk controller 14 determines whether or not therespective sectors can be updated based on the information.

EXAMPLE 4

[0088] Hereinafter, the fourth example of the present invention will bedescribed with reference to FIG. 5. In FIG. 5, since the referencenumerals 1 to 18 denote the same components as those having the samereference numerals in the first example, the description thereof will beomitted herein. In addition, since the reference numerals 9 to 26correspond to and have the same configurations as the reference numerals4 to 7 and 9 to 12 in FIG. 5, respectively, the description thereof willalso be omitted herein. In FIG. 5, the reference numeral 27 denotes aframe decimator; 28 denotes a frame interpolator; and 29 denotes a thirdswitch.

[0089] The hard disk apparatus 8 has at least two recording regions. Thefirst recording region is a region in which the video signal received bythe tuner 2 is recorded and which realizes the function described in thefirst example. Assuming that the first recording region has a capacitylarge enough to record compressed video signals corresponding to twohours, if the viewer does not start watching a program within two hoursafter the recording start time, the video data which was recordedpreviously is updated from the point of time, whereby a videocorresponding to two hours preceding the time when the viewer startswatching the recorded video can always be watched as a normal video asalready described in the first example.

[0090] In this example, when the video data is updated, the previouslyrecorded video data is once read out; passed through the buffer memories23 and 24; and then decoded by the decoder 26 into the original videosignals. Then, a frame decimator 27 performs frame decimation processingwith respect to these decoded video signals, thereby reducing the amountof data. The output of the frame decimator 27 is compressed again by theencoder 19. The compressed video signal, a part of the frames of whichhave been decimated in this way, are saved in the second recordingregion. The resulting recordable time is varied depending upon themethod for decimating the frames. For example, assuming that thecompression is performed by extracting one frame out of four frames, arecordable time four times as long as the recordable time in the case ofrecording a normally compressed video signal can be secured by using thesame recording capacity. That is to say, when a hard disk apparatushaving a recording capacity large enough to record data corresponding to2.5 hours by a normal recording operation is used, the viewer can watcha broadcast preceding the recording start time by about four hours(i.e., two hours in the first recording region and two hours in thesecond recording region) and check the contents of the broadcast. As aresult, the viewer can confirm a larger amount of the contents of theprograms while using a smaller recording capacity. In other words, whilereducing the required minimum recording capacity of a hard diskapparatus, it is also possible to meet the viewer's demand for recordinga video as long as possible.

[0091] It is natural that the audio signals recorded in the secondrecording region are normally recorded without performing a decimationoperation on a frame basis. When the video signals recorded in thesecond recording region are read out to be displayed on the TV monitor13, the output of the decoder 12 shown in FIG. 5 is once input to theframe interpolator 28, where the decimated frames are interpolated bythe same frames and the interpolated signals are passed through thethird switch 29 so as to be displayed on the TV monitor 13. In thisexample, a frame decimation method is used for reducing the amount ofvideo data. Alternatively, various other methods such a sampling methodand a color difference signal elimination method can also be used.

[0092] In this example, the hard disk apparatus is divided into tworecording regions for simplifying the description. However, a circuitfor applying information for identifying whether the video data recordedon the hard disk is data composed of normally recorded video signals, ordata having a reduced amount of data by a frame decimation or the liketo the video data recorded on the hard disk, and saving the dataincluding the identifiers on the hard disk, may be provided. Forexample, it is possible to utilize a method in which the type ofrecorded data, the sector information and the like are recorded in thetable RAM 15 shown in FIG. 5 and the hard disk controller 14 controlsthe hard disk apparatus 8 based on the information.

[0093] In addition, the viewer can independently set a time periodduring which a video signal is normally recorded and a time periodduring which data is recorded after the amount of the data is reduced bya frame decimation or the like. As a result, the viewer can utilize theapparatus of the invention so as to satisfy his own preferences morecompletely.

EXAMPLE 5

[0094] Hereinafter, the fifth example of the present invention will bedescribed. Since the fundamental configuration used in this example isthe same as that shown in FIG. 1, there are no drawings exclusively usedfor describing this example. If a plurality of (i.e., a number N of)tuners having the same configuration as the tuner 2 shown in FIG. 1 areprovided, a plurality of video signals can be simultaneously received. Anumber N of encoders 4 may be provided. Alternatively, if an encoder ofthe type operating at an encoding rate N times as high as a normalencoding rate is used, then it is possible to use the encoder byswitching it depending upon the time.

[0095] If a number N of hard disk apparatuses having the sameconfiguration as that of the hard disk apparatus 8 shown in FIG. 1 areused in parallel; if the reading and writing rates from/onto the harddisk apparatus 8 are set to be higher while using a single hard diskapparatus 8 in the same way as in FIG. 1; or if the period A1, A2, A3, .. . or the capacity of the buffer memories is increased such that thetime T_(N) required for reading and writing in the N channels becomesshorter than the period, then it is possible to read out a video on adesired channel while simultaneously writing videos on the N channels.By realizing this function, a viewer can select his desired another TVchannel after a TV program on a channel to be watched is finishedwithout designating the another channel beforehand.

EXAMPLE 6

[0096] Hereinafter, the sixth example of the present invention will bedescribed with reference to FIG. 6. In FIG. 6, since the referencenumerals 1 to 18 denote the same components as those having the samereference numerals in the first example, the description thereof will beomitted herein.

[0097] In FIG. 6, the reference numeral 30 denotes a screen synthesizer;31 denotes a screen separator; and 32 denotes a pixel interpolator. Inthis example, by providing a plurality of (e.g., four in FIG. 6) tuners2 and demodulators 3, a plurality of video signals can be simultaneouslyreceived. The received video signals are input to the screen synthesizer30. The screen synthesizer 30 matches the phases of the synchronizingsignals of the respective video signals by using frame memories (notshown) and then reduces the sizes of the screens corresponding to therespective video signals by performing a pixel decimation, a linedecimation and the like, thereby synthesizing the screens having reducedsizes into one screen as shown in FIG. 7. A composite video signalobtained by synthesizing the video signals in the above-described manneris compressed by the encoder 4 and then recorded onto the hard diskapparatus 8 in the same way as in the first example. In performing areproducing operation, the screen separator 31 extracts only the portioncorresponding to the desired channel from the synthesized screen and thepixel interpolator 32 performs a pixel interpolation and a lineinterpolation on the extracted portion for enlarging the size of theportion to that of a normal screen and then displays the video on the TVmonitor 13, as shown in FIG. 8. FIG. 8 is a diagram illustrating anoperation of retrieving only the video in the desired channel from thereproduced video. As a result, videos on a larger number of TV channelscan be recorded in the hard disk apparatus 8 having the same recordingcapacity as that of a conventional one. In addition, by reading out avideo on a desired channel while simultaneously writing videos on the Nchannels, a viewer can select his desired another TV channel after a TVprogram on a channel to be watched is finished without designating theanother channel beforehand. Furthermore, in this sixth example, it isnot necessary to use an N-times-larger recording capacity for recordingthe videos in the N channels, unlike the third example, so that it iseffectively possible to save the recording capacity of the hard diskapparatus.

[0098] It is naturally possible to directly display the composite videosignal output from the decoder 12 without performing a screenseparation.

[0099] In the foregoing examples, a recording format (or a relationshipbetween a GOP unit and a sector unit on the hard disk, in particular)has not been specifically described. However, in view of the case ofperforming a trick-play reproducing operation such as a fast-forwardreproducing operation, it is preferable to utilize a format in which asimple relationship is established between a GOP and a sector. Forexample, a format in which one GOP consists of a number K of sectors; aformat in which one sector consists of a number M (where K and M areintegers) of GOPs; a format in which a number K of sectors correspond toa number M of GOPs; or the like can be used.

[0100] In addition, if the hard disk apparatus of the present inventionis configured as a hard disk apparatus having a removable drive portionwhich is currently used as a peripheral device for a personal computer,then the hard disk apparatus of the present invention can beadvantageously used for forming a backup file of video data, savingparticular video data and the like.

[0101] Various other modifications will be apparent to and can bereadily made by those skilled in the art without departing from thescope and spirit of this invention. Accordingly, it is not intended thatthe scope of the claims appended hereto be limited to the description asset forth herein, but rather that the claims be broadly construed.

What is claimed is:
 1. A video signal recording and reproducingapparatus comprising: receiving means for receiving a television signal;image compression means for compressing an amount of information perunit time of the received continuous video signal; writing means forintermittently writing a compressed video signal, obtained as an outputof the image compression means, onto a hard disk apparatus via amagnetic head; reading means for intermittently reading out the writtencompressed video signal from the hard disk apparatus via the magnetichead; decoding means for restoring the read compressed video signal intoan original video signal; display means for displaying the restoredvideo signal; and control means for controlling the writing means andthe reading means such that writing the video signal onto the hard diskapparatus and reading an arbitrary video signal, which was previouslywritten onto the hard disk apparatus, from the hard disk apparatus areperformed apparently simultaneously and continuously.
 2. A video signalrecording and reproducing apparatus according to claim 1 , wherein acompressed video signal which was recorded at an earliest time issequentially updated by a newly received and obtained compressed videosignal.
 3. A video signal recording and reproducing apparatus accordingto claim 1 , wherein an audio signal, as well as a compressed videosignal, is recorded onto the hard disk apparatus.
 4. A video signalrecording and reproducing apparatus according to claim 1 , furthercomprising instruction means for starting and/or finishing recording acompressed video signal onto the hard disk apparatus.
 5. A video signalrecording and reproducing apparatus according to claim 1 , furthercomprising instruction means for starting and/or finishing reproducing acompressed video signal from the hard disk apparatus.
 6. A video signalrecording and reproducing apparatus according to claim 4 , wherein theinstruction means for starting recording a compressed video signal ontothe hard disk apparatus is instantaneously driven manually.
 7. A videosignal recording and reproducing apparatus according to claim 4 ,wherein the instruction means for starting recording a compressed videosignal onto the hard disk apparatus is driven by timer means.
 8. A videosignal recording and reproducing apparatus according to claim 4 ,wherein the instruction means for finishing recording a compressed videosignal onto the hard disk apparatus is driven by timer means.
 9. A videosignal recording and reproducing apparatus according to claim 5 ,wherein the instruction means for starting reproducing a compressedvideo signal from the hard disk apparatus is instantaneously drivenmanually.
 10. A video signal recording and reproducing apparatusaccording to claim 1 , wherein the display means displays at least atime difference between a time at which a video signal which is beingreproduced was recorded and a current time, in addition to a video. 11.A video signal recording and reproducing apparatus according to claim 1, wherein the display means displays at least a current time and a timeat which a video signal which is being reproduced was recorded, inaddition to a video.
 12. A video signal recording and reproducingapparatus according to claim 1 , comprising operation means for settinga normal reproduction, a fast forward reproduction, a backwardreproduction or a slow reproduction as a reproduction mode.
 13. A videosignal recording and reproducing apparatus according to claim 1 ,wherein the display means simultaneously displays a received videosignal and an output of the decoding means which was previouslyrecorded, reproduced and decoded.
 14. A video signal recording andreproducing apparatus according to claim 1 , further comprisingtelevision signal detection means for determining whether or not thereceiving means has received a normal television signal, wherein writingonto the hard disk apparatus is enabled only when the television signaldetection means has detected a normal television signal.
 15. A videosignal recording and reproducing apparatus comprising: image compressionmeans for digitizing an input continuous video signal and audio signal,thereby compressing an amount of information per unit time; writingmeans for intermittently writing a compressed video signal, obtained asan output of the image compression means, onto a hard disk apparatus viaa magnetic head; reading means for intermittently reading out thewritten compressed video signal from the hard disk apparatus via themagnetic head; decoding means for restoring the read compressed videosignal into an original video signal; and display means for displayingthe restored video signal, thereby reading out predetermined video andaudio signals at a predetermined time.
 16. A video signal recording andreproducing apparatus comprising: image compression means for digitizingan input continuous video signal and audio signal, thereby compressingan amount of information per unit time; writing means for intermittentlywriting a compressed video signal, obtained as an output of the imagecompression means, onto a hard disk apparatus via a magnetic head;reading means for intermittently reading out the written compressedvideo signal from the hard disk apparatus via the magnetic head;decoding means for restoring the read compressed video signal into anoriginal video signal; display means for displaying the restored videosignal; and sound recognition means for recognizing an audio signal,wherein predetermined video and audio signals are read out at a point oftime when the sound recognition means recognizes a predetermined sound.17. A video signal recording and reproducing apparatus comprising: imagecompression means for digitizing an input continuous video signal andaudio signal, thereby compressing an amount of information per unittime; writing means for intermittently writing a compressed videosignal, obtained as an output of the image compression means, onto ahard disk apparatus via a magnetic head; reading means forintermittently reading out the written compressed video signal from thehard disk apparatus via the magnetic head; decoding means for restoringthe read compressed video signal into an original video signal; anddisplay means for displaying the restored video signal, wherein a videosignal at an arbitrary point of time is retrieved for an arbitrary timeperiod by an operation of a viewer from video signals which are beingreceived or video signals which were previously recorded, andinformation for prohibiting overwriting data of the retrieved videosignal is added to the retrieved video signal so as to be stored intothe hard disk apparatus.
 18. A video signal recording and reproducingapparatus according to claim 17 , wherein, when a video signal retrievedby an operation of a viewer is saved, search information required forthe viewer to search for a desired video signal later is added to thevideo signal to be saved, and after the video signal which waspreviously retrieved and saved has been searched for and read out basedon the search information, the read compressed video signal is decodedto be displayed on the display means.
 19. A video signal recording andreproducing apparatus according to claim 17 , comprising at least anoutput terminal for outputting digital data which has been recorded ontothe hard disk apparatus to the outside of the apparatus, wherein a videosignal retrieved by a viewer is transferred to another recordingapparatus through the output terminal.
 20. A video signal recording andreproducing apparatus comprising: image compression means for digitizingan input continuous video signal and audio signal, thereby compressingan amount of information per unit time; writing means for intermittentlywriting a compressed video signal, obtained as an output of the imagecompression means, onto a hard disk apparatus via a magnetic head;reading means for intermittently reading out the written compressedvideo signal from the hard disk apparatus via the magnetic head;decoding means for restoring the read compressed video signal into anoriginal video signal; and display means for displaying the restoredvideo signal, wherein, while compressing a video signal which is beingreceived and writing the compressed video signal onto the hard diskapparatus, a video signal which was previously recorded is read out anddecoded into an original video signal, and wherein, after an amount ofdata of the decoded video signal has been reduced, the video signal issubjected to an image compression again and written onto the hard diskapparatus.
 21. A video signal recording and reproducing apparatuscomprising: receiving means for simultaneously receiving televisionsignals from a plurality of channels; image compression means forcompressing an amount of information per unit time of the receivedcontinuous video signals from the plurality of channels; writing meansfor intermittently writing each compressed video signal, obtained as anoutput of the image compression means, onto a hard disk apparatus via amagnetic head; reading means for intermittently reading out the writtencompressed video signal from the hard disk apparatus via the magnetichead; decoding means for restoring the read compressed video signal intoan original video signal; and display means for displaying the restoredvideo signal, wherein, while compressing video signals from theplurality of channels which are being received and writing thecompressed video signals onto the hard disk apparatus, a video signalwhich was previously recorded from a particular channel is read out. 22.A video signal recording and reproducing apparatus comprising: receivingmeans for simultaneously receiving television signals from a pluralityof channels; synthesis means for synthesizing the received televisionsignals from the plurality of channels into one screen; imagecompression means for compressing an amount of information per unit timeof the continuous video signal which has been synthesized by thesynthesis means; writing means for intermittently writing a compressedvideo signal, obtained as an output of the image compression means, ontoa hard disk apparatus via a magnetic head; reading means forintermittently reading out the written compressed video signal from thehard disk apparatus via the magnetic head; decoding means for restoringthe read compressed video signal into an original video signal; anddisplay means for displaying the restored video signal, wherein aplurality of video signals are synthesized into one screen, subjected toan image compression and then written onto the hard disk apparatus.